The present invention relates to an iron tip of an electric soldering iron, and more particularly to an iron tip for an electric soldering iron, having a base material surface modified into a surface of Cuxe2x80x94Al alloy of high Al concentration in order to have resistance to oxidation under high temperature environment, and a soldering iron.
Soldering is a general method for connection and bonding in electronic and other industries. Soldering is roughly classified into mass soldering (batch soldering) and manual soldering.
Mass soldering includes a flow soldering method of mounting elements and components on a printed circuit board, and then immersing the board in a molten solder bath, and a reflow soldering method (SMT) of kneading solder particles and flux with a binder, printing the mixed solder paste on the junction area of the printed circuit board, and then mounting components. Both of the methods have the following feature: it is possible to simultaneously solder multiple points.
On the other hand, manual soldering is mainly performed by using a soldering iron, and multiple points cannot be soldered simultaneously. However, the manual soldering is a traditional method and has the following feature: anybody can perform it easily. Besides, for repair of defective joints of mass soldering, the soldering iron method is indispensable. Recently, in particular, use of Pb-free solder is increasing in the face of pollution problems, and defective joints are increasing due to poor soldering performance as compared with the conventional Snxe2x80x94Pb solder, and correction by soldering iron is becoming more and more important, and the soldering iron is playing a more important role than ever.
A conventional electric soldering iron device will be described. FIG. 1 is an exploded perspective view of a main part at a leading end side of a conventional electric soldering iron. As shown in the figure, a ceramic heater 5 is inserted into a hollow space (a shell 8 in FIG. 3) opened at a base end side formed in an iron tip 3, a protective pipe 2 is fitted on the iron tip 3, and then a cap nut 1 fitted in the protective pipe 2 has been tightened into a nipple 6. At this time, a stainless steel insert pipe 4 having the same length as the ceramic heater 5 is fitted into the hollow space of the iron tip 3. It is thus assembled as shown in FIG. 2 and put in use. In this structure, when the iron tip 3 is worn in a long period of use, it can be easily replaced with a new tip.
A sectional view of a conventional iron tip 3 is shown in FIG. 3. The material of the iron tip is required to transfer the heat of the ceramic heater 5 instantly to the tip leading end portion 3a, and hence pure copper of excellent heat conduction or highly heat conductive copper alloy is used.
The surface of the copper-made iron tip 3 is coated with Fe plating 7 of tens of microns in thickness, and further in other areas than the leading end portion 3a, Cr plating 10 of several microns in thickness is applied. The leading end portion 3a is coated with a solder alloy 9, and soldering is done here. At this time, the Fe plating 7 is intended to suppress excessive solder attack of the pure copper or copper alloy material, and the Cr plating 10 is intended to protect the surface from corrosion after Fe plating and prevent oxidation at a high temperature.
On the other hand, in a rear end portion 3b at the opposite side of the leading end portion 3a, a cylindrical shell 8 incorporating a bar-shaped ceramic heater 5 is formed, and it can be freely detached from the heater 5. In the shell 8, further, a stainless steel insert pipe 4 is fitted along the inside, and it protects the ceramic heater 5 from contact with oxide scale formed inside.
However, the conventional structure involved many problems as listed below, and it has been desired to improve them.
First, the Cr plating 10 applied on the outermost layer of the iron tip 3 contains hexavalent chromium in its plating solution, discharge of its wastewater is controlled by the pollution control law, and it is demanded to convert to other plating not using Cr, or other surface treatment than plating.
Structurally, when the iron tip 3 is fitted into the ceramic heater 5 and heated, the inside of the shell of the iron tip 3 is considerably oxidized by the presence of an air layer, and oxide scales of CuO or Cu2O are formed, and heat conduction is impaired and short circuit or other troubles are caused.
Moreover, since the iron tip 3 can be freely detached, a narrow gap is formed between the inside of the insert pipe 4 and the periphery of the ceramic heater 5, and temperature control with high precision is difficult due to temperature difference caused by it. As its countermeasure, as mentioned above, the thin stainless steel insert pipe 4 is placed between the shell 8 of the iron tip 3 and the ceramic heater 5, but considerable oxidation of the base material copper cannot be avoided, and the stainless steel pipe is poor in heat conductivity and shields the heat conduction, and the response of the temperature sensor is lowered.
In order to solve the problems, an iron tip for an electric soldering iron, composed of copper or copper alloy, wherein a part or all of an outer surface excluding a leading end portion of the iron tip is modified into a surface with a Cuxe2x80x94Al alloy coating layer.
An electric soldering iron comprising an iron tip composed of copper or copper alloy, wherein a part or all of an outer surface excluding a leading end portion of the iron tip is modified into a surface with a Cuxe2x80x94Al alloy coating layer.
Here, in the iron tip for a soldering iron, a Cuxe2x80x94Al alloy coating layer having a high Al concentration is formed on a surface, and a rigid film of aluminum oxide Al2O3 is formed, thereby providing resistance to oxidation at high temperature.